Catheter having an improved distal tip

ABSTRACT

An elongated balloon catheter having a distal tip member on the distal end of the catheter and having a sleeve surrounding and secured at least to the proximal end of the distal tip member.

This application is a divisional of currently pending U.S. Ser. No.11/172,543, filed Jun. 29, 2003; which is a continuation of patentapplication U.S. Ser. No. 10/002,613, filed Nov. 1, 2001, which issuedas U.S. Pat. No. 6,918,920 B1, on Jul. 19, 2005.

FIELD OF INVENTION

This invention generally relates to medical devices, and particularly tointraluminal balloon catheters having improved distal tips.

BACKGROUND OF THE INVENTION

In percutaneous transluminal coronary angioplasty (PTCA) procedures, aguiding catheter is advanced until the distal tip of the guidingcatheter is seated in the ostium of a desired coronary artery. Aguidewire, positioned within an inner lumen of a dilatation catheter, isfirst advanced out of the distal end of the guiding catheter into thepatient's coronary artery until the distal end of the guidewire crossesa lesion to be dilated. Then the dilatation catheter having aninflatable balloon on the distal portion thereof is advanced into thepatient's coronary anatomy, over the previously introduced guidewire,until the balloon of the dilatation catheter is properly positionedacross the lesion.

Once properly positioned, the dilatation balloon is inflated with liquidone or more times to a predetermined size at relatively high pressures(e.g. greater than 8 atmospheres) so that the stenosis is compressedagainst the arterial wall and the wall expanded to open up thepassageway. Generally, the inflated diameter of the balloon isapproximately the same diameter as the native diameter of the body lumenbeing dilated so as to complete the dilatation but not overexpand theartery wall. After the balloon is finally deflated, blood flow resumesthrough the dilated artery and the dilatation catheter can be removed.

In such angioplasty procedures, there may be restenosis of the artery,i.e. reformation of the arterial blockage, which necessitates eitheranother angioplasty procedure, or some other method of repairing orstrengthening the dilated area. To reduce the restenosis rate and tostrengthen the dilated area, physicians frequently implant anintravascular prosthesis, generally called a stent, inside the artery atthe site of the lesion. Stents are usually delivered to a desiredlocation within a coronary artery in a contracted condition on a balloonof a catheter which is similar in many respects to a balloon angioplastycatheter, and expanded to a larger diameter by expansion of the balloon.The balloon is deflated to remove the catheter and the stent left inplace within the artery at the site of the dilated lesion.

Catheters designed for intravascular procedures such as angioplasty havea number of design considerations. Such catheters must be able totransmit force along the length of the catheter shaft so that thecatheter can be pushed through the patient's vasculature. However, thecatheter shaft must also have sufficient flexibility to allow thecatheter to track over a guidewire through tortuous vasculature as wellas crossing stenosed portions of the vascular anatomy.

Prior art intravascular catheters have commonly included a soft distaltip to prevent or minimize injury to the vessel during advancement ofthe catheter therein. One difficulty has been forming a connectionbetween the soft tip and the catheter which is sufficiently strong toprevent disengagement of the soft tip or kinking at the junction betweenthe soft tip and catheter shaft. Additionally, it is necessary tobalance the strength of the connection between the soft tip and thecatheter shaft with the need to minimize the stiffness of the distal endof the catheter. Minimizing the stiffness of the distal end of thecatheter results in improved maneuverability of the catheter.

Accordingly, it would be a significant advance to provide a catheterwith a soft tip having improved performance. This invention satisfiesthese and other needs.

SUMMARY OF THE INVENTION

The present invention is directed to a balloon catheter with improveddistal extremity. The catheter includes an elongated catheter shafthaving a proximal end, a distal end, and proximal and distal shaftsections. A guidewire receiving lumen extends along at least a distalportion of the catheter shaft to a port provided at the distal end ofthe catheter shaft. An inflation lumen extends along at least a portionof the catheter shaft terminating at a point proximal to the distal endof the catheter shaft.

An inflatable member, such as a balloon with proximal and distal endsand an interior chamber, is disposed on the distal catheter shaftsection. The interior chamber of the balloon is in fluid communicationwith the inflation lumen extending within the catheter shaft. Theballoon further includes a distal shaft portion or skirt which issealingly secured to the portion of the catheter shaft extending throughthe interior chamber of the balloon. The catheter has a soft tip memberwhich is secured to the distal end of the portion of the catheterextending through the interior of the balloon and which has an innerlumen which is in fluid communication with the guidewire receiving lumenof the catheter shaft. A polymeric sleeve is secured to the proximal endof the soft tip member and may also be secure to a distal end of theportion of the catheter shaft which extends beyond the distal end of thedistal balloon shaft. The sleeve may be heat or fusion bonded oradhesively bonded, preferably by a UV-curable adhesive to the underlyingmember or members.

A balloon catheter having features of the invention exhibits improvedtensile characteristics with excellent flexibility.

These and other advantages of the invention will become more apparentfrom the following detailed description when taken in conjunction withthe accompanying exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view, partially in section, of a ballooncatheter embodying features of the invention.

FIG. 2 is an enlarged elevational view, partially cutaway, of the distalportion of the catheter shown in FIG. 1.

FIG. 3 is a transverse cross-section of the catheter of FIG. 2 takenalong lines 3-3.

FIG. 4 is a transverse cross-section of the catheter of FIG. 2 takenalong lines 4-4.

FIG. 5 is an elevational view partially in section of an alternativeembodiment in which the outer sleeve on the distal tip is tapered in thedistal direction to smaller transverse dimensions.

FIG. 6 is a partial longitudinal cross-sectional view of an alternativedesign of the distal tip of the catheter shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 through 4 illustrate a balloon catheter 10 embodying features ofthe invention, which include an elongated catheter shaft 11 havingproximal and distal shaft sections 12 and 13 respectively, an inflatableballoon 14 on the distal catheter shaft section and a distal tip member15 secured to the distal end 16 of a portion of the catheter shaft thatextends through the interior chamber 17 of the balloon 14. A flexiblesleeve 18 is secured to the exterior of the distal end 16 and the distaltip member 15. An adapter 19 is provided on the proximal shaft section12 for directing inflation fluid, and the like to and from the catheter10.

In the embodiment best illustrated in FIGS. 2-4, the distal shaftsection 13 has an outer tubular member 20 with an inflation lumen 21extending therethrough, and an inner tubular member 22 with a guidewirereceiving lumen 23 disposed within the inflation lumen 21 for slidablyreceiving a guidewire 24. Balloon 14 has proximal balloon shaft sectionor skirt 25 and a distal balloon shaft section or skirt 26 and acylindrical working section 27. Proximal and distal tapers 28 and 29respectively extend from the ends of the working section 27 to theballoon shaft sections 25 and 26 as shown. The inner tubular member 22extends through the balloon interior 17 and has distal end 15 whichextends through the distal balloon shaft section and preferably slightlybeyond thereof.

The proximal balloon shaft section 25 is sealingly secured to the distalend of outer tubular member 20 and the distal balloon shaft section 26is sealingly secured to the distal portion 27 of the inner tubularmember 22. Sleeve 18 is secured to the distal end 16 of the innertubular member 22 which extends beyond the distal end of the balloondistal shaft section 26 and the proximal end 30 of distal tip member 15.The distal tip member 15 has an inner lumen which forms in part theguidewire lumen 23 and is preferably has the same inner diameter as theportion of the guidewire lumen 23 within the inner tubular member 22.

FIG. 5 illustrates an alternative design of the distal extremity of thecatheter 10 wherein the distal tip member 15 and the sleeve 18 taper inthe distal direction to smaller transverse dimensions. A stent 32 isshown mounted on the exterior of the balloon working section 27.

FIG. 6 illustrates an alternative catheter construction wherein thedistal tip member 15 has a proximal portion which extends over thedistal end 16 of the inner tubular member 22. In this embodiment thesleeve 18 is secured only to the exterior of the distal tip member 15,but the sleeve 18 extends over the portion of the distal end 16 of theinner tubular member 22 which extends beyond the end of the distalballoon shaft section 26. The sleeve 18 and distal tip member 15 may becoextruded together, preferably from compatible polymeric materials toform a single tubular member. The outer layer forming the sleeve 18 maybe removed by suitable means from the exterior distal portion of thetubular member and the inner portion may be removed from the proximalportion to facilitate mounting over the distal end 16.

In one catheter design embodying features of the invention, the distaltip member 15 has a length of about 1 to about 10 mm, preferably about2.5 to about 5 mm and typically about 2.5 to about 3.5 mm. The length ofsleeve 18 should range from about 1 to about 10 mm; preferably about 1to about 5 mm and typically about 1.5 to about 2.5 mm. The distal end 16of the catheter shaft 11 (or inner tubular member 22) may be flush withthe distal end of the distal balloon shaft section 26 or extend distallyfrom the distal end of the distal balloon shaft section 26 a distancenot more than about 20 mm, preferably not more than about 10 mm.Typically, the distal end 16 will extend about 0.25 to about 0.5 mm fromthe distal balloon shaft section.

The distal tip member 15, has a wall thickness ranging from about 0.0025to about 0.005 inch (0.06-0.13 mm), preferably, from about 0.003 toabout 0.004 inch (0.08-0.1 mm), The sleeve 18 may have a wall thicknessof about 0.0015 to about 0.005 inch (0.04-0.13 mm), preferably about0.002 to about 0.003 inch (0.05-0.08 mm).

The dimensions of balloon catheter 10 are determined largely by the sizeof the artery or other body lumen through which the catheter must passor the size of the stent being delivered. Typically, the outer tubularmember 20 has an outer diameter of about 0.02 to about 0.045 inch (0.5to 1.1 mm), typically about 0.037 inch (0.94 mm), an inner diameter ofabout 0.015 to about 0.035 inch (0.38 to 0.89 mm), typically about 0.03inch (0.76 mm). The wall thickness of the outer tubular member 20 canvary from about 0.002 to about 0.008 inch (0.051 to 0.201 m), typicallyabout 0.003 inch (0.076 mm). The inner tubular member 22 typically hasan outer diameter of about 0.016 to about 0.03 inch (0.4-0.8 mm),typically about 0.021 inch (0.5 mm). The overall working length of thecatheter 10 may range from about 100 to about 150 centimeters (cm), andis typically about 147 cm. Preferably, balloon 14 may have a workinglength about 0.5 cm to about 4 cm and typically about 2 cm with aninflated working diameter of about 1 to about 8 mm, and for coronaryapplications about 1 mm to about 5 mm. The cylindrical wall forming theworking length 27 of the balloon 14 has a thickness ranging from about0.001 to about 0.003 inch (0.03-0.08 mm), preferably, from about 0.0015to about 0.002 inch (0.04-0.05 mm).

The dimensions, such as wall thickness, of the various cathetercomponents may vary depending upon the strength and flexibilitycharacteristics of the material from which the catheter components areformed. Moreover, the wall thickness of the catheter components may alsovary, if they are tapered such as the distal tip member and sleeve shownin FIG. 5.

The various catheter components can be formed of suitable conventionalmaterials. The inner tubular member and outer tubular member, arepreferably formed of material, or include material thereon, which iscompatible with the balloon material to allow formation of appropriatebonding therebetween. Similarly, the sleeve and the distal tip memberare preferably formed of compatible materials for essentially the samereason.

In one design embodying features of the invention, the distal tip member15 is of a soft tip design configured to provide an atraumatic distalend on the catheter to minimize injury to the patient's vasculatureduring advancement of the catheter therein. The distal tip member andsleeve are preferably formed of a polymeric material having a Shoredurometer hardness of about 80A to about 90D, preferably about 40D toabout 75D. Suitable materials include PEBAX (a polyether block amide) orPELLETHANE (a polyurethane). The Shore hardness of the sleeve 18 may beless than or greater than the Shore hardness of the distal tip member15, but preferably is less, e.g. with PEBAX the Shore hardness may be40D for the sleeve 18, verses 55D for the distal tip member 15. However,the distal tip member may be formed of a variety of polymeric materialsincluding polyethylene based adhesives such as PRIMACOR, high densitypolyethylene (HDPE), polyurethane, and polyesters such as HYTREL.However, the choice of material depends on a variety of factorsincluding the desired application and the method used to make the distaltip member 15 and the sleeve.

To the extent not discussed herein, the various catheter components canbe formed of conventional materials. Outer tubular member 20 and theinner tubular member 22 can be formed by conventional techniques, forexample by extruding, from materials already found useful inintravascular catheters such a polyethylene, polyvinyl chloride,polyesters, polyamides, polyimides, polyetherether ketone (PEEK) andcomposite or blends of these materials. The various components may bejoined by heat or fusion bonding or use of suitable adhesives,particularly UV cured adhesives.

A variety of balloon catheter designs may be used, including rapidexchange, over-the-wire, and fixed wire catheter designs. A rapidexchange catheter generally includes a distal guidewire port in thedistal end of the catheter shaft, a proximal guidewire port spaced asubstantial distance distal to the proximal end of the catheter shaftand at least about 4, preferably at least 10 cm from the distal end ofthe catheter, and a guidewire lumen extending between and in fluidcommunication with the proximal and distal guidewire ports. Asillustrated in FIG. 5, the balloon catheter of the invention may be usedto deliver prostheses, such as expandable stents, grafts, and the like,to a desired location within the patient's vasculature. The stent 32,schematically shown in FIG. 5, comprises an expandable tubular body,typically having an open-walled structure, which is mounted on balloon34 so that upon inflation of the balloon the stent will be expanded andseated against the interior of the vessel wall. Additionally, catheter10 may be used to tough up a previously implanted stent by positioningballoon within a stent lumen and expanding the balloon to further expandthe stent within a body lumen.

While particular designs embodying features of the invention have beenillustrated and described herein, it will be apparent to those skilledin the art that various modifications can be made to the invention.Moreover, those skilled in the art will recognize that feature found inone embodiment may be utilized in another embodiment. Terms such as“elements”, “members”, “devices” and words of similar import when usedherein shall not be construed as invoking the provisions of 35 U.S.C.§112(6) unless the following claims expressly use the term “means” or“step” followed by a particular function.

Accordingly, it is not intended that the invention be limited, except asby the appended claims.

1. A balloon catheter, comprising: a. an elongated catheter shaft whichhas a proximal catheter shaft section, a distal catheter shaft section,an inflation lumen, a guidewire receiving lumen extending along at leasta portion of the distal shaft section in communication with a guidewiredistal port at the distal end of the catheter, and a balloon on thedistal catheter shaft section having an interior in fluid communicationwith the inflation lumen of the shaft, and having an inflatable section,and proximal and distal balloon skirt sections secured to the cathetershaft; b. a distal tip member mounted on and bonded to an outer surfaceof the distal catheter shaft section, which has a proximal section witha proximal portion forming a lap joint over the distal end of thecatheter shaft, a distal section located distal to the distal end of theshaft having a distal end defining the guidewire distal port, and aninner lumen in fluid communication with the guidewire receiving lumen ofthe shaft; and c. a polymeric sleeve which has a proximal end, and adistal end, and which is disposed about and secured to the proximalsection of the distal tip member so that the distal end of the sleeve islocated distal to the catheter shaft distal end and proximal to thedistal tip distal end, and the proximal end of the sleeve is locatedproximal to the catheter shaft distal end, and the sleeve tapersdistally so that the distal end of the sleeve has an outer diameter lessthan the proximal end of the sleeve.
 2. The balloon catheter of claim 1,wherein a distal end of the distal balloon skirt section has the sameouter diameter as the proximal end of the sleeve.
 3. The ballooncatheter of claim 2, wherein the distal balloon skirt section isdistally tapered.
 4. The balloon catheter of claim 3 wherein theproximal end of the sleeve abuts the distal end of the distal balloonskirt section.
 5. The balloon catheter of claim 3 wherein the shaftdistal end is located distal to the distal end of the balloon distalskirt section.
 6. The balloon catheter of claim 1 wherein the sleeve isformed of material which is compatible with material of which the distaltip member is formed.
 7. The balloon catheter of claim 6 wherein thesleeve and distal tip member comprise a coextruded tube.
 8. The ballooncatheter of claim 6 wherein the sleeve is formed of a polymeric materialselected from the group consisting of polyether block amide andpolyurethane.
 9. The balloon catheter of claim 1 wherein the sleeve isformed of a polymeric material having a Shore hardness between about 80Aand 90D.
 10. The balloon catheter of claim 1 wherein the sleeve isformed of a polymeric material having a Shore hardness between about 40Dand 65D.
 11. The balloon catheter of claim 1 wherein the distal tipmember is formed of a polymeric material having a Shore hardness betweenabout 80A and 90D.
 12. The balloon catheter of claim 1 wherein thedistal tip member is formed of a polymeric material having a Shorehardness between about 40D and 65D.
 13. The catheter of claim 1 whereinthe distal tip member is formed of a polymeric material selected fromthe group consisting of a polyether block amide, a polyester, apolyethylene based adhesives, high density polyethylene, polyurethane.